1. Field of the Invention
The present invention relates to an electronic musical instrument utilizing microprocessor control and more specifically to a system for communicating data among the microprocessors which control the electronic musical instrument whereby data is communicated synchronously to assure accurate data transfer and to minimize the time required for communication.
2. Description of the Prior Art
Some electronic musical instruments capable of sounding automatic accompaniment rhythms and sequences, generating chords in response to the playing of a key, and providing other musical functions utilize microprocessors to control the operation of the instrument to accomplish these functions. One such system, for example, is described in U.S. patent application Ser. No. 040,107 entitled "Automatic Control Apparatus for Chords and Sequences," filed May 8, 1979 now U.S. Pat. No. 4,292,874 and assigned to Baldwin Piano and Organ Company. As the number of desired control functions to be performed by the microprocessors increases to provide additional instrument features, the capability of a single microprocessor is exceeded and it becomes necessary to utilize two or more microprocessors to provide all of the functions desired in an instrument. Thus, various operations can be divided up among the microprocessors, and a greater number of functions can be provided by utilizing additional microprocessors. In a single instrument, however, it is necessary that the various microprocessors interact with each other so that operations are performed at the proper time and notes ultimately are sounded at the appropriate times to create the desired music. In addition, interaction among the microprocessors increases their efficiency by permitting data to be shared, thereby eliminating the expenditure of time and capacity in duplicating operations performed by another of the microprocessors. The present invention provides a system of data communication among microprocessors to satisfy the foregoing needs of providing additional functions with greater efficiency.